unsupported_media_type

HTTP 415 · The request body was not JSON.

What causes it

A request with a body arrived without `Content-Type: application/json`.

What to do

Set the header. Most HTTP clients do not set it for you.

Retry?

No — the same request produces the same answer.

The response

{
  "type": "https://developers.vaki.co/errors/unsupported_media_type",
  "title": "…",
  "status": 415,
  "code": "unsupported_media_type",
  "detail": "…",
  "instance": "/v1/checkout_links"
}

Branch on code, never on title or detail. The full list of codes, and the shape of the problem document, is on Errors.